A glass or glass-ceramic sealant is described for a SOFC having a coefficient of thermal expansion in the range of from about 8 to about 13{times}10{sup {minus}6}/C and a viscosity of at least 10{sup 3}Pa-s at cell operating temperature. The sealant has a composition of SrO present in the range of from about 5 to about 60 mole percent, La{sub 2}O{sub 3} present in the range of from 0 to about 45 mole percent, Al{sub 2}O{sub 3} present in the range from 0 to about 15 mole percent, B{sub 2}O{sub 3} present in the range of from about 15 mole percent to about 80 mole percent, and SiO{sub 2} present in the range of from 0 to about 40 mole percent, wherein the material is a viscous fluid at cell operating temperatures of from about 600 C to about 1000 C. The sealant may also be compounds of CaO present in the range of from 0 to about 35 mole percent, Al{sub 2}O{sub 3} present in the range from 0 to about 15 mole percent, B{sub 2}O{sub 3} present in the range of from about 35 mole percent to about 85 mole percent, and SiO{sub 2} present in the rangemore » of from 0 to about 30 mole percent. 2 figs.« less

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A glass or glass-ceramic sealant for a SOFC having a coefficient of thermal expansion in the range of from about 8 to about 13.times.10.sup.-6 /.degree.C. and a viscosity of at least 10.sup.3 Pa-s at cell operating temperature. The sealant has a composition of SrO present in the range of from about 5 to about 60 mole percent, La.sub.2 O.sub.3 present in the range of from 0 to about 45 mole percent, Al.sub.2 O.sub.3 present in the range from 0 to about 15 mole percent, B.sub.2 O.sub.3 present in the range of from about 15 mole percent to about 80 molemore » percent, and SiO.sub.2 present in the range of from 0 to about 40 mole percent, wherein the material is a viscous fluid at cell operating temperatures of from about 600.degree. C. to about 1000.degree. C. The sealant may also be compounds of CaO present in the range of from 0 to about 35 mole percent, Al.sub.2 O.sub.3 present in the range from 0 to about 15 mole percent, B.sub.2 O.sub.3 present in the range of from about 35 mole percent to about 85 mole percent, and SiO.sub.2 present in the range of from 0 to about 30 mole percent.« less

Basic requirements for a sealant are good bonding to the materials of interest, chemical stability in the operating environment, and low gas permeability. For high-temperature operation as in Solid Oxide Fuel Cells (SOFCs), the sealant must also have a thermal expansion which is reasonably close to that of the other materials involved and must have some compliance, or softness, to allow for some mismatch between the components to be joined. In this paper, we discuss a family of glass-ceramic materials with mechanical, chemical, and electrical properties that are suitable for these demanding high-temperature applications.

A family of sealant materials has been developed for use in the solid oxide fuel cell (SOFC) and in other applications in the temperature range of 800{endash}1000{degree}C. These materials are based on glasses and glass-ceramics in the SrO{endash}La{sub 2}O{sub 3}{endash}Al{sub 2}O{sub 3}{endash}B{sub 2}O{sub 3}{endash}SiO{sub 2} system. The coefficients of thermal expansion (CTE) for these materials are in the range of 8{endash}13{times}10{sup {minus}6}/{degree}C, a good match with those of the SOFC components. These sealant materials bond well with the ceramics of the SOFC and, more importantly, form bonds that can be thermally cycled without failure. At the fuel cell operating temperature,more » the sealants have viscosities in the range of 10{sup 4}{minus}10{sup 6} Pa-s, which allow them to tolerate a CTE mismatch of about 20{percent} among the bonded substrates. The gas tightness of a sample seal was demonstrated in a simple zirconia-based oxygen concentration cell. {copyright} {ital 1996 Materials Research Society.}« less

An electrode supported electrolyte membrane includes an electrode layer 630 facing an electrolyte layer 620. The opposing side of the electrode layer 630 includes a backing layer 640 of a material with a thermal expansion coefficient approximately equal to the thermal expansion coefficient of the electrolyte layer 620. The backing layer 640 is in a two dimensional pattern that covers only a portion of the electrolyte layer 630. An electrochemical cell such as a SOFC is formed by providing a cathode layer 610 on an opposing side of the electrolyte layer 620.

A key issue in developing commercially viable planar solid oxide fuel cell stacks is appropriate seal design. We are currently developing an alternative approach to rigid and compressive seal designs that conceptually combines advantages of both techiques, including hermeticity, mechanical integrity, and minimization of interfacial stresses in either of the joint substrate materials, particulary the ceramic. The new seal relies on a plastically deformable metal seal; one that offers a quasi-dynamic mechanical response in that it is adherent to both sealing surfaces, i.e. non-sliding, but readily yields or deforms under thermally generated stresses, thereby mitigating the development of stresses inmore » the adjacent ceramic and metal components even when a significant difference in thermal expansion exists between the two materials. Here we employ finite element modeling to assess the potential thermal cycling performance of this design, specifically as it pertains to sealing components with vastly different thermal expansion properties.« less

August 2005, Narottam P. Bansal; The American Ceramic Society, Westerville, OH, United States(US).

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